sort

Sort text files.
Sort, merge, or compare all the lines from the files given (or standard input.)

Syntax
sort [options...] [file...]
Options
sort has three modes of operation:
Sort (the default), Merge (-m), and Check(-c)
-c Check whether the given files are already sorted: if they are
not all sorted, print an error message and exit with a status of 1.
-m Merge the given files by sorting them as a group. Each input
file should already be individually sorted. It always works to
sort instead of merge; merging is provided because it is faster,
in the case where it works.
Ordering Options: (these affect the order of output lines)
-b Ignore leading blanks when finding sort keys in each line.
-d Sort in dictionary `phone directory' order: ignore all characters except
letters, digits and blanks when sorting.
-f Fold lower case characters into the equivalent upper case characters
when sorting so that, for example, `b' is sorted the same way `B' is.
-i Ignore characters outside the ASCII range 040-0176 octal (inclusive)
when sorting.
-M An initial string, consisting of any amount of white space, fol-
lowed by three letters abbreviating a month name, is folded to
UPPER case and compared in the order `JAN' < `FEB' < ... <
`DEC.' Invalid names compare low to valid names.
-n Compare according to arithmetic value an initial numeric string
consisting of optional white space, an optional - sign, and zero
or more digits, optionally followed by a decimal point and zero
or more digits.
-r Reverse the result of comparison, so that lines with greater key
values appear earlier in the output instead of later.
Other options:
-o output-file
Write output to output-file instead of to standard output.
If output-file is one of the input files, sort copies it to a
temporary file before sorting and writing the output to output-
file.
-t separator
Use character separator as the field separator when finding the
sort keys in each line. By default, fields are separated by the
empty string between a non-whitespace character and a whitespace
character. That is to say, given the input line ` foo bar',
sort breaks it into fields ` foo' and ` bar'. The field separa-
tor is not considered to be part of either the field preceding
or the field following it.
-u For the default case or the -m option, only output the first of
a sequence of lines that compare equal. For the -c option,
check that no pair of consecutive lines compares equal.
+POS1 [-POS2]
Specify a field within each line to use as a sorting key. The
field consists of the portion of the line starting at POS1 and
up to (but not including) POS2 (or to the end of the line if
POS2 is not given). The fields and character positions are num-
bered starting with 0.
-k POS1[,POS2]
An alternate syntax for specifying sorting keys. The fields and
character positions are numbered starting with 1.
sort --help
sort --version

A position has the form f.c, where f is the number of the field to use
and c is the number of the first character from the beginning of the
field (for +pos) or from the end of the previous field (for -pos). The
.c part of a position may be omitted in which case it is taken to be
the first character in the field. If the -b option has been given, the
.c part of a field specification is counted from the first nonblank
character of the field (for +pos) or from the first nonblank character
following the previous field (for -pos).

A +pos or -pos argument may also have any of the option letters Mbdfinr appended to it, in which case the global ordering options are not used
for that particular field.

The -b option may be independently attached
to either or both of the +pos and -pos parts of a field specification,
and if it is inherited from the global options it will be attached to
both.

If a -n or -M option is used, thus implying a -b option, the -b option is taken to apply to both the +pos and the -pos parts of a key
specification.

Keys may span multiple fields.

The
Ordering Options may be
specified globally or as part of a specific key field. If no key
fields are specified, global options apply to comparison of entire lines;
otherwise the global options are inherited by key fields that do not
specify any special options of their own.

The Apple man page for sort includes GNU long options for all the above, but these have not (yet) been implemented under OSX.

HOW LINES ARE COMPARED

A pair of lines is compared as follows: if any key fields have been
specified, sort compares each pair of fields, in the order specified on
the command line, according to the associated ordering options, until a
difference is found or no fields are left.

If any of the global options Mbdfinr are given but no key fields are
specified, sort compares the entire lines according to the global options.

Finally, as a last resort when all keys compare equal (or if no ordering options were specified at all), sort compares the lines byte by
byte in machine collating sequence. The last resort comparison honors
the -r global option. The -s (stable) option disables this last-resort
comparison so that lines in which all fields compare equal are left in
their original relative order. If no fields or global options are
specified, -s has no effect.

GNU sort has no limits on input line length or restrictions on bytes
allowed within lines. In addition, if the final byte of an input file
is not a newline, GNU sort silently supplies one.

If the environment variable TMPDIR is set, sort uses it as the directory in which to put temporary files instead of the default, /tmp. The -Ttempdir option is another way to select the directory for temporary
files; it overrides the environment variable.

A file name of - means standard input.

By default, sort writes the results to the standard output.

"We never sit anything out. We are cups, constantly and quietly being filled. The trick is, knowing how to tip ourselves over and let the Beautiful Stuff out" ~ Ray Bradbury